Catadioptric projection systems

ABSTRACT

Catadioptric projection systems are disclosed for projecting an illuminated region of a reticle onto a corresponding region on a substrate. The systems are preferably used with ultraviolet light sources (e.g., 193 nm). The systems comprise a first imaging system, a concave mirror, and a second imaging system. The first imaging system comprises a single-pass lens group and a double-pass lens group. The single-pass lens group comprises a first negative subgroup, a positive subgroup, and a second negative subgroup. Light from the illuminated region of the reticle passes through the single-pass lens group and the double-pass lens group, and reflects from the concave mirror to pass back through the double-pass lens group to form an intermediate image of the illuminated region of the reticle. The light is then directed to the second imaging system that re-images the illuminated region of the reticle on the substrate. Alternatively, light from the single-pass lens group is reflected by a turning mirror to the double-pass lens group, wherein the light returning through the double-pass lens group continues directly to the second imaging system.

This application claims the benefit of Japanese patent application no.8- 149903, filed May 20, 1996, and is a continuation in part of U.S.patent application Ser. No. 08/212,639, filed Mar. 10, 1994 and whichissued as U.S. Pat. No. 5,636,066, U.S. patent application Ser. No.08/628,165, filed Apr. 25, 1996 and which issued as U.S. Pat. No.5,689,377, U.S. patent application Ser. No. 08/552,453, filed Nov. 3,1995 and which issued as U.S. Pat. No. 5,691,802, U.S. patentapplication Ser. No. 08/429,970, filed Apr. 27, 1995 and which issued asU.S. Pat. No. 5,808,805 and is currently pending as U.S. reissueapplication Ser. No. 09/764,157, U.S. patent application Ser. No.08/515,631, filed Aug. 16, 1995 and which issued as U.S. Pat. No.5,861,997 and is currently pending as U.S. reissue application Ser. No.09/766,486, which correspondingly claim priority under 35 U.S.C. Section119 (a)-(d) to Japanese patent application no. 5 - 051718, filed Mar.12, 1993, Japanese patent application no. 5 - 137641, filed Jun. 8,1993, Japanese patent application no. 7 - 082380, filed Apr. 7, 1995,Japanese patent application no. 8 - 030978, filed Feb. 19, 1996,Japanese patent application no. 6 - 271631, filed Nov. 7, 1994, Japanesepatent application no. 7 - 047142, filed Mar. 7, 1995, Japanese patentapplication no. 7 - 177858, filed Jul. 14, 1995, Japanese patentapplication no. 6 - 090837, filed Apr. 28, 1994, and Japanese patentapplication no. 6 - 198350, filed Aug. 23, 1994.

FIELD OF THE INVENTION

This invention pertains to catadioptric projection systems suitable foruse with ultraviolet light sources and applicable to steppers andmicrolithography systems for the manufacture of semiconductors andliquid crystal display panels.

BACKGROUND OF THE INVENTION

Semiconductor device geometries continue to grow smaller. Because themanufacture of semiconductor devices requires the transfer ofhigh-resolution circuit patterns be transferred to semiconductor wafers,the microlithography systems that project these circuit patterns ontosemiconductor wafers must form high-resolution images.

The resolution of microlithography systems has been improved in severalways. For example, high-resolution microlithography systems useultraviolet light instead of visible light and have high numericalaperture optical systems.

Various types of high-resolution optical projection systems have beenconsidered for high-resolution microlithography systems. Purelyrefractive projection systems are inadequate al at ultravioletwavelengths. For wavelengths below 300 nm, only a few optical materialsare transmissive and refractive optical elements generally must be madeof either synthetic fused quartz or fluorite. Unfortunately, combiningoptical elements of synthetic fused quartz and fluorite is ineffectivein eliminating chromatic aberration because the Abbe numbers ofsynthetic quartz and fluorite are not sufficiently different. Therefore,refractive optical systems for wavelengths less than about 300 nm sufferfrom unacceptable levels of chromatic aberration.

Fluorite itself suffers from several disadvantages. The refractive indexof fluorite changes relatively rapidly with temperature and fluoritepolishes poorly. Therefore, most ultraviolet optical systems do not usefluorite, and thus exhibit uncorrected chromatic aberration.

Purely reflective projection systems avoid these difficulties, but areflective projection system typically requires a large diameter mirror;frequently, the mirror must be aspheric. Because the manufacture ofprecision aspheric surfaces is extremely difficult, a reflectiveprojection system using an aspheric mirror is prohibitively expensive.

Catadioptric projection systems have also been used. A catadioptricprojection system is a projection system that uses both reflectiveelements (mirrors) and refractive elements (lenses). Many catadioptricprojection systems for microlithography systems form at least oneintermediate image within the optical system. Examples include thecatadioptric projection systems of Japanese laid-open patent documents5-25170 (1993), 63-163319 (1988), and 4-234722 (1992), and U.S. Pat. No.4,779,966.

Japanese laid-open patent document 4-234722 (1992) and U.S. Pat. No.4,779,966 describe catadioptric projection systems comprising a concavemirror and double-pass lens groups having negative power. In thesesystems, an incident light beam propagates through the double-pass lensgroup in a first direction, strikes the concave mirror, and thenpropagates as a reflected light beam through the double-pass lens groupin a second direction opposite to the first direction. In theseprior-art systems, the double-pass lens groups have negative power. Forthis reason, light incident to the concave mirror is divergent and thediameter of the concave mirror must be large.

The double-pass optical system of Japanese laid-open patent document4-234722 (1992) is symmetric; aberrations in this optical system areextremely low, simplifying aberration correction in the subsequentrefractive optical system. However, because it is symmetric, the opticalsystem has a short working distance. In addition, because it isdifficult with this system to separate the incident light beam and thereflected light beam, a beamsplitter is required. The preferablelocation for the beamsplitter in such a projection system is near theconcave mirror. Consequently, the beamsplitter is large, heavy, andexpensive.

The optical system of U.S. Pat. No. 4,779,966 comprises a concave mirrorin a second imaging system. In this system, diverging light enters theconcave mirror and the concave mirror must have a large diameter.

Optical systems comprising more than one mirror can use fewer lensesthan a purely refractive optical system, but other problems arise. Inorder to increase resolution and depth of focus, phase-shift masks arefrequently used. In order to effectively use a phase-shift mask, theratio a σ of the numerical aperture of the irradiation optical systemand the numerical aperture of the projection system should be variable.While an adjustable aperture is easily located in the irradiationoptical system, a catadioptric projection system usually has no suitablelocation for a corresponding aperture, adjustable or not.

In a catadioptric projection system in which a double-pass lens group isplaced within a demagnifying portion of the optical system, thedemagnification reduces the distance between the reflecting elements andthe semiconductor wafer. This limits the number of lens elements thatcan be inserted in the optical path, and thus limits the numericalaperture of the projection system and the total optical power availableto expose the wafer. Even if a high numerical aperture is possible theworking distance (i.e., the distance between the wafer and the mostimagewise surface of the optical system) is short.

Prior-art catadioptric projection systems have optical elements arrangedalong more than one axis, using prisms or mirrors to fold the opticalpathway. The alignment of optical elements in a system with more thanone axis is expensive and difficult, especially when high resolution isrequired. Prior-art catadioptric projection systems are also difficultto miniaturize while simultaneously maintaining image quality. Inaddition, in a miniaturized prior-art catadioptric projection system,the beam-separation mirror that separates the incident light beam fromthe reflected light beam is likely to obstruct one of these beams.

Increasing the magnification of the intermediate image and moving thebeam-separation mirror away from the optical axis have been consideredas solutions to this problem. However, changing the magnification of theintermediate image requires changes to the remainder of the opticalsystem to maintain an appropriate magnification on the wafer. Thiscauses loss of image quality.

Moving the beam-separation mirror away from the optical axis withoutchanging the magnification of the intermediate image can be accomplishedby using light beams propagating farther off-axis and increasing thediameter of the projection system. Both of these changes areundesirable, leading to a larger, heavier projection system with lessresolution.

Some prior-art catadioptric projection systems are used in full-fieldexposure systems in which patterns from an entire reticle are projectedonto the wafer in a single exposure. Examples include the catadioptricprojection systems of Japanese laid-open patent documents 2-66510(1990), 3-282527 (1991), and 5-72478 (1993), and U.S. Pat. No.5,089,913. These systems have a beamsplitter (or a partially reflectingmirror) placed near a concave mirror. The beamsplitter directs light tothe concave mirror and to the wafer. Because the light is divergent nearthe concave mirror, the beamsplitter must be large. Large beamsplittersmade of prisms are expensive and difficult to manufacture; plate-typebeamsplitters are difficult to keep precisely planar. Large prisms haveother disadvantages, including their weight and the difficulty ofobtaining suitable raw material for their manufacture. A largebeamsplitter tends to degrade image quality because of non-uniformreflectance, phase change, and absorption. For ultraviolet projectionsystems, a prism beamsplitter tends to have low transmittance.

In view of the foregoing, improved catadioptric projection systems formicrolithography systems are needed.

SUMMARY OF THE INVENTION

This invention provides catadioptric projection systems that are readilyminiaturized while maintaining image quality. A catadioptric projectionsystem according to this invention comprises a first imaging system anda second imaging system. The first imaging system comprises asingle-pass lens group and a double-pass lens group including a concavemirror. Light from an illuminated region of the reticle returns throughthe single-pass lens group and then enters the double-pass lens group.Light propagates through the double-pass lens group in a firstdirection, strikes the concave mirror, and then returns through thedouble-pass lens group in a second direction opposite the firstdirection. A turning mirror is provided between the single-pass lensgroup and the double-pass lens group. In some embodiments of theinvention, the turning mirror directs the light from the first imagingsystem (after reflection by the concave mirror and back through thedouble-pass lens group) to the second imaging system. In alternativeembodiments of the invention, the turning mirror directs light exitingthe single-pass lens group to the double-pass lens group. The firstimaging system forms an intermediate image of the illuminated region ofthe reticle near the turning mirror; the second imaging system re-imagesthe intermediate image and forms an image of the illuminated region ofthe reticle on a substrate, typically a semiconductor wafer.

In such catadioptric projection systems, the diameter of the concavemirror can be kept small, the ratio of the imaging-optical-systemnumerical aperture and the illumination-optical-system numericalaperture σ can be variable, and an appropriate location is available foran aperture if phase-shift masks are used. In addition, suchcatadioptric projection systems have high numerical apertures and henceprovide sufficient irradiation to the wafer as well as conveniently longworking distances.

The second imaging system comprises a first lens group and a second lensgroup.

The single-pass lens group comprises, in order starting at the reticle,a first negative subgroup, a positive subgroup, and a second negativesubgroup. Single-pass optical groups with this configuration arecompact, producing high-resolution images, and permit separation ofincident and reflected light beams. The magnification of the firstimaging system can be selected as appropriate while still maintainingexcellent optical performance. Thus, the magnification of theintermediate image can be varied. Preferably, either the first imagingsystem or the second imaging system demagnifies the reticle. Obtaining ademagnification using the first imaging system simplifies the secondimaging system.

The first negative subgroup preferably comprises a lens with a concavesurface facing the reticle. The second negative subgroup preferablycomprises a lens element with a concave surface facing the double-passlens group.

In one example embodiment, the first imaging system further comprisesanother turning mirror that receives light transmitted by thesingle-pass lens group and directs the light along an axis of thedouble-pass lens group. This embodiment permits the reticle and thewafer to be on substantially the same optical axis.

In another example embodiment, the second imaging system comprisesfurther comprises a turning mirror placed between the first lens groupand the second lens group. This turning mirror receives light from thefirst lens group and directs the light along an axis of the second lensgroup. This embodiment permits the reticle and wafer to be in parallelplanes.

Embodiments of the invention in which the reticle and wafer are inparallel planes or are along the same axis simplify wafer exposure inscanning systems. It will be readily apparent that the inventionincludes other arrangements of turning mirrors.

The foregoing and other objects, features, and advantages of theinvention will become more apparent from the following detaileddescription which proceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general schematic representation of an optical systemaccording to the invention.

FIG. 2 shows a catadioptric projection system according to a firstexample embodiment of the invention.

FIG. 3 is a detailed drawing of the first example embodiment of FIG. 2with the catadioptric projection system unfolded for simplicity.

FIG. 4 contains graphs of transverse aberrations of the optical systemof the first example embodiment at various image heights.

FIG. 5 shows a catadioptric projection system according to a secondexample embodiment of the invention.

FIG. 6 shows a catadioptric projection system according to a thirdexample embodiment of the invention.

FIG. 7 is a general schematic representation of a prior-art opticalsystem.

DETAILED DESCRIPTION

For purposes of describing the invention, a “lens element” is a singlelens (i.e., a single piece of “glass”); a lens “group” or “subgroup”comprises one or more lens elements. A positive lens, lens group, orsubgroup has a positive focal length; a negative lens, lens group, orsubgroup has a negative focal length. An “optical axis” is a straightline through centers of curvature of surfaces of optical elements. Aswill be apparent, an optical system can have more than one optical axis.Distances from an off-axis point to an optical axis are measured along aline through the point and perpendicular to the optical axis.

In order to describe the invention, a representation of a prior-artoptical system is first described with reference to FIG. 7. A ray 102from a location on a reticle R a distance d from an optical axis 100 isincident on a lens group A₁. The lens group A₁ comprises, in order fromthe reticle R and along the optical axis 100, a positive subgroup A₁₂and a negative subgroup A₁₃. The lens group A₁ bends the ray 102 towardthe optical axis 100 so that the height b of the ray 102 as it exits thenegative subgroup A₁₃ is reduced. For this reason, the optical path ofthe ray 102 is easily blocked by a mirror M₂ placed after the negativesubgroup A₁₃.

The present invention avoids this problem. With reference to FIG. 1, aray 202 from a location on a reticle R a distance d from an optical axis200 is incident to a lens group A₁ comprising, in order from the reticleR, a first negative subgroup A₁₁, a positive subgroup A₁₂, and a secondnegative subgroup A₁₃. The first negative subgroup A₁₁, bends the ray202 away from the optical axis 200. The positive subgroup A₁₂ then bendsthe ray 202 towards the optical axis 200. The height a of the ray 202exiting the second negative subgroup A₁₃ is thus increased in comparisonwith the prior-art system of FIG. 7, thereby reducing the likelihood ofobstruction of the ray 202 by a mirror M₂.

Because rays from the reticle R are more distant from the optical axis200, the lens group A₁ of FIG. 1 reduces the possibility of obstructionof rays from the reticle R by the mirror M₂. Optical systems using suchlens groups can be more compact and provide enhanced image quality incomparison with prior-art optical systems.

FIG. 2 shows a first example embodiment of the invention. The firstexample embodiment provides a catadioptric projection system thatprojects a demagnified image of a circuit pattern from an illuminatedregion 221 (FIG. 2(a)) of a reticle R onto a semiconductor wafer W. Theillumination region 221 is illuminated by an illumination opticalsystem, not shown in FIG. 2. Such a projection system can project apattern onto other substrates as well, such as a glass panel for aliquid crystal display, and it is apparent that the invention is notlimited to systems for projecting circuit patterns onto semiconductorwafers. (Thus, it will be understood that “wafer” as used hereinencompasses any of various appropriate substrates onto which an image,defined by the reticle R, can be projected.) In the example embodimentspresented herein, the optical projection systems are intended for use atwavelengths around 193 nm but it will be apparent that the invention isalso applicable to other wavelengths.

The optical projection system (FIG. 2(b)) of the first exampleembodiment comprises a first imaging system A that receives light fromthe illuminated region 221 of the reticle R and forms an intermediateimage of the illuminated region. The optical projection system furthercomprises a turning mirror M₂ placed near the intermediate image and asecond imaging system B that receives light reflected by the turningmirror M₂. The second imaging system B re-images the intermediate imageonto a corresponding region 231 on the wafer W (FIG. 2(c)).

The first imaging system A comprises a single-pass lens group A₁ and adouble-pass lens group A₂. In order from the reticle R and along anoptical axis 210, the single-pass lens group A₁ comprises a firstnegative subgroup A₁₁ comprising a negative lens with a concave surfacefacing toward the reticle R and a positive lens. Continuing along theoptical axis 210 from the first negative subgroup A₁₁, the single-passlens group A₁ further comprises a positive subgroup A₁₂ comprisingpreferably a single positive lens element, and a second negativesubgroup A₁₃ comprising a negative lens element with a concave surfacefacing the double-pass lens group A₂. The second negative subgroup A₁₃is the closest of the subgroups of the single-pass lens group A₁ to thedouble-pass lens group A₂.

The double-pass lens group A₂ is placed along the optical axis 210 andreceives light from the single-pass lens group A₁ and directs light to aconcave mirror M₁ of the double-pass optical group A₂, placed on theoptical axis 210. The concave mirror M₁ reflects light back through thedouble-pass lens group A₂. After passing through the double-pass lensgroup A₂, the light forms an image near the turning mirror M₂. Theturning mirror M₂ reflects light from the first imaging system A to thesecond imaging system B. The turning mirror M₂ directs light propagatingalong the optical axis 210 to propagate along an optical axis 211 of thesecond imaging system.

The second imaging system B comprises, beginning near the turning mirrorM₂ and proceeding along the optical axis 211, a first lens group B₁ anda second lens group B₂. An aperture S is placed between the first lensgroup B₁ and the second lens group B₂.

FIG. 3 shows the optical system of the first embodiment in detail. Forclarity, the folded optical path caused by the concave mirror M₁ and theturning mirror M₂ has been unfolded by inserting virtual flat mirrorsimmediately behind the concave mirrors M₁ and the turning mirror M₂.These virtual mirrors are not actually part of the first exampleembodiment but serve to simplify FIG. 3. Such an unfolded representationof a catadioptric optical system will be readily understood by personsof ordinary skill in the art.

Table 1 contains specifications for the first example embodiment. InTable 1, the first column lists surface numbers, numbered from thereticle R to the wafer W. Surface numbers relevant to this discussionare specifically denoted in FIG. 3. The second, third, and fourthcolumns of Table 1 list the radii of curvature of the optical surfaces(“r”), surface separations (“d”) along the optical axis, and the lensmaterial, respectively. The fifth column indicates the group number foreach of the optical elements. Distances are in mm. Some of the surfacesof Table 1 represent plane mirrors and other planar surfaces used tosimplify FIG. 3; such surfaces do not represent actual optical elements.

Table 1 lists the elements of the double-pass lens group A₂ twice.Surfaces indicated as part of the lens group A₂ are surfaces throughwhich pass light propagates immediately after propagating through thesingle-pass lens group A₁; the same surfaces through which the lightpropagates immediately after reflection from the concave mirror M₁ areindicated as belonging to the lens group A₂*. As will be apparent, theconcave mirror M₁ is included only once.

The lenses of the first embodiment are made of synthetic fused quartz(SiO₂) and fluorite (CaF₂). Axial chromatic aberration and chromaticdifference of magnification (lateral color) are corrected for awavelength range of ±0.1 nm about a wavelength of 193 nm for use with anultraviolet excimer laser emitting at a wavelength of 193 nm. The Abbenumbers ν₁₉₃ given are for fluorite and synthetic fused quartz atwavelengths of 193 nm ±0.1 nm instead of the customary visiblewavelengths; the refractive indices n are for a wavelength of 193 nm.

As specified in Table 1, the optical projection system of the firstexample embodiment provides a demagnification of the reticle R on thewafer W of ¼, a wafer-side numerical aperture of 0.6, and covers a spanof 76 mm of the reticle R.

TABLE 1 (First Example Embodiment) Lens Material Properties Index ofRefraction Abbe Number Material (n) ν₁₉₃ Fused Quartz 1.56019 1780(SiO₂) Fluorite 1.50138 2550 (CaF₂) Optical System Specifications Surf.No. r d Material Group 0 — 70.000000 R 1 −497.01528 15.000000 CaF₂ A₁₁ 2−2089.03221 0.100000 3 4955.40172 35.000000 SiO₂ A₁₁ 4 −684.523030.100000 5 373.53254 40.000000 SiO₂ A₁₂ 6 −458.84391 32.494228 7−384.75862 15.000000 SiO₂ A₁₃ 8 399.06352 11.499839 9 ∞ 0 10 ∞ 15.00000011 ∞ 0 12 ∞ 30.000000 13 ∞ 0 14 ∞ 15.805933 15 360.53651 60.00000 CaF₂A₂ 16 −357.18478 1.00000 17 −410.75622 15.00000 SiO₂ A₂ 18 272.782523.000000 19 264.76319 55.000000 CaF₂ A₂ 20 −403.51844 8.000000 21−313.01237 15.000000 SiO₂ A₂ 22 −536.13663 141.754498 23 753.9396916.200000 SiO₂ A₂ 24 350.20343 24.941513 25 502.28185 22.5000000 SiO₂ A₂26 1917.58499 72.939269 27 696.45818 25.920000 CaF₂ A₂ 28 422.4415445.000000 29 −165.29930 15.000000 SiO₂ A₂ 30 −247.15361 7.435835 31447.76970 40.000000 SiO₂ A₂ 32 −650.53438 176.819005 33 −207.0325715.000000 SiO₂ A₂ 34 3807.25755 27.000000 35 ∞ 0 36 316.26451 27.000000(M₁) A₂ 37 −3807.25755 15.000000 SiO₂ A₂* 38 207.03257 176.819005 39650.53438 45.000000 SiO₂ A₂* 40 −447.76970 7.435035 41 247.1536115.000000 SiO₂ A₂* 42 165.29930 45.000000 43 −422.44154 25.920000 CaF₂A₂* 44 −696.45818 72.939269 45 −1917.58499 22.500000 SiO₂ A₂* 46−502.28185 24.941513 47 −350.20343 16.20000 SiO₂ A₂* 48 −753.93969141.754498 49 536.13663 15.000000 SiO₂ A₂* 50 313.01237 8.000000 51403.51844 55.000000 CaF₂ A₂* 52 −264.76319 3.000000 53 −272.7825215.000000 SiO₂ A₂* 54 410.75622 1.000000 55 357.18478 60.000000 CaF₂ A₂*56 −360.53651 15.805933 57 ∞ 0 58 ∞ 30.000000 59 ∞ 0 60 ∞ 130.000000 M₂61 408.08942 20.000000 SiO₂ B₁ 62 203.49020 3.000000 63 207.5268430.000000 CaF₂ B₁ 64 19354.35793 0.1000000 65 429.85442 35.000000 SiO₂B₁ 66 −403.83438 14.478952 67 −353.07980 15.000000 SiO₂ B₁ 68 261.2496831.363884 69 −219.57807 23.000000 SiO₂ B₁ 70 −348.23898 1.990938 71502.56605 40.000000 CaF₂ B₁ 72 −747.25197 421.724019 73 638.7357229.16000 SiO₂ B₁ 74 −809.39570 0.079197 75 316.55680 32.805000 SiO₂ B₁76 309.57052 15.000000 77 — 54.627545 S 78 213.28576 51.714104 CaF₂ B₂79 −7409.32571 13.778100 80 −616.12401 39.000000 SiO₂ B₂ 81 −1209.660820.373771 82 472.08983 39.000000 SiO₂ B₂ 83 1043.43948 0.267894 84103.01598 49.409891 SiO₂ B₂ 85 77.85822 9.349712 86 81.54405 32.465682CaF₁ B₂ 87 6656.48506 3.061800 88 −400.35184 13.094819 SiO₂ B₂ 89−922.72813 1.399628 90 1101.31959 16.951746 SiO₂ B₂ 91 −554.932131.641793 92 1392.34272 16.702978 SiO₂ B₂ 93 3939.24661 15.000000 94 ∞ W

FIG. 4 provides graphs of transverse aberrations of the first exampleembodiment for several values of image height Y at three wavelengths. Asis apparent from FIG. 4, the transverse aberrations are well-correctedeven at the full numerical aperture.

In the first example embodiment, the optical projection system does notproject the entire reticle R onto the wafer W in a single exposure.Rather, as shown in FIG. 2(a), an illuminated region 221 of the reticleR is projected onto a corresponding exposure region 231 on the wafer W(FIG. 2(c)). In the first embodiment, the illuminated region 221 isrectangular, 120 mm long and 24 mm wide. The length of the illuminatedregion 221 is symmetrically placed with respect to a line 222perpendicular to the optical axis 210. The width of the illuminatedregion 221 is such that the illuminated region 221 extends from 52 mm to76 mm from a line 223 perpendicular to the optical axis 210.

The pattern from the entire reticle R is transferred to the wafer W bysynchronously scanning both the reticle R and the wafer W duringexposure of the wafer W. Arrows 241, 242 indicate the scan directionsfor the reticle R and the wafer W, respectively. It will be apparentthat other shapes and sizes of the illuminated region can be used.

In the first example embodiment, the turning mirror M₂ so receives lightreflected by the concave mirror M₁ and directs the light to the secondimaging system B. The invention also provides an alternative arrangementin which the turning mirror M₂ receives light from the single-pass lensgroup and directs the light to the double-pass lens group and theconcave mirror M₁. Light reflected by the concave mirror M₂ thenpropagates directly to the second imaging system without reflection bythe turning mirror M₁. In the first example embodiment and in such amodification of the first example embodiment, the turning mirror M₁ thusseparates light propagating from the double-pass optical group A₂ andlight propagating to the double-pass optical group A₂.

A second example embodiment of the invention is shown in FIG. 5. Theoptical projection system of FIG. 5 is similar to that of the embodimentof FIG. 2. Light from an illuminated region 321 (FIG. 3(a)) of a reticleR is directed to, beginning nearest the reticle R and along an opticalaxis 310, a single-pass lens group A₁ comprising a first negativesubgroup A₁₁, a positive subgroup A₁₂ and a second negative subgroupA₁₃. After the second negative subgroup A₁₃, a turning mirror MO M₀reflects the light along an optical axis 311 of a double-pass lens groupA₂ including a concave mirror Ml M₁. Light is transmitted by thedouble-pass lens group A₂ and is reflected by the concave mirror M₁ backthrough the double-pass lens group A₂ to a turning mirror M₂. Anintermediate image of the illuminated region 321 is formed near theturning mirror M₂.

The turning mirror M₂ directs the light from the illumi-natedilluminated region of the reticle R along the optical axis 310 which isan optical axis of the second imaging system B as well as of thesingle-pass lens group A₁. The second imaging system B receives lightfrom the turning mirror M₂ and re-images the intermediate image onto acorresponding region 331 on the wafer W. As will be apparent, the secondembodiment differs from the first embodiment in that the turning mirrorM₀ is placed between the single-pass lens group A₁ and the double-passlens group A₂. The turning mirror M₀ permits the reticle R and the waferW to be in parallel planes. As shown in FIG. 5, the reticle R and thewafer W are along the same optical axis 312.

With reference to FIG. 6, an optical system according to a third exampleembodiment of the invention differs from the first embodiment in that aturning mirror M₃ is placed between the first lens group B₁ and thesecond lens group B₂ of the second imaging system B. As a result of thereflection by the turning mirror M₃, the optical system of the thirdexample embodiment transfers a pattern from an illuminated region 421 ofthe reticle R (FIG. 6(a)) to the wafer W wherein the reticle R and thewafer W are in parallel planes. Unlike the second example embodiment,the wafer W and the reticle R of the third example embodiment are onseparate optical axes 401, 402 of the first imaging system A and thesecond lens group B₂ of the second imaging system B, respectively.

In the third example embodiment, the turning mirror M₂ receives lightreflected by the concave mirror M₁ and directs the light to the secondimaging system B. The invention also provides an alternative arrangementin which the turning mirror M₂ receives light from the single-pass lensgroup and directs the light to the double-pass lens group and theconcave mirror M₁. Light reflected by the concave mirror M₂ thenpropagates directly to the second imaging system without reflection bythe turning mirror M₁.

The first, second, and third example embodiments are similar to eachother, but differing in respect to the number and placement of turningmirrors. Therefore, these example embodiments provide the same imagequality.

In each of the example embodiments described above, the single-pass lensgroup A₁ comprises a first negative subgroup, a positive subgroup, and asecond negative subgroup. The catadioptric projection systems of thisinvention are readily miniaturized with no loss of image quality. WhileFIGS. 2, 5, and 6 show a scanning exposure of the wafer W, thecatadioptric projection systems of this invention can also be used forfull-field exposure.

The catadioptric projection systems of the present invention includeseveral other favorable characteristics. First, a turning mirror (or abeamsplitter) can be placed near the intermediate image, therebyreducing the size of the turning mirror. Second, unlike conventionalcatadioptric projection systems that allow light reflected by a mirrorto overlap with the incident light (which makes placement of theaperture S difficult), the catadioptric projection systems of thepresent invention allow the aperture S to be placed in the secondimaging system B so that the ratio of the numerical apertures of anirradiation optical system to the catadioptric projection system σ canbe easily varied. Third, by increasing the number of lens elements inthe second imaging system B, the numerical aperture of the catadioptricprojection system according to the invention can be increased. Fourth,re-imaging the intermediate image by the second imaging system Bprovides a long working distance. Fifth, the catadioptric projectionsystems of the invention are compact. Finally, because light reflectedfrom the concave mirror M₁ is returned near the focused image, off-axislens aberrations are reduced.

With the additional turning mirrors of the second and third exampleembodiments, the relative orientations of the reticle R and the wafer Wcan be adjusted. I.e., the second example embodiment, the reticle R andwafer W are parallel to each other and on the same optical axis. In thethird example embodiment, the reticle R and the wafer W are parallel toeach other but are situated on offset but parallel optical axes. Thus,the present invention permits orienting the reticle R and the wafer W ina way allowing simplification of the scanning systems.

The catadioptric projection systems of the example embodiments alsopermit the turning mirrors to closely approach the respective opticalaxes. Therefore, light reflected by the concave mirror M₁ back throughthe double-pass lens group A₂ is easily separated from the lightpropagating from the single-pass lens group A₁ to the double-pass lensgroup A₂. Because the turning mirror or mirrors are situated close tothe respective optical axes, light need not propagate at large angleswith respect to the optical axes and off-axis aberrations are reduced.Prior-art systems often require angles of 20° or more while thecatadioptric projection systems of this invention use angles no greaterthan about 10°.

Some prior-art scanning projection systems expose an annulus of thewafer from a corresponding annular illuminated region of the reticle.The reticle and wafer are scanned at different speeds corresponding tothe magnification of the optical projection system. Because suchscanning exposure systems expose only small areas of the wafer W at anygive instant, complete exposure of the wafer W requires many incrementalexposures. If the light from a radiation source is used inefficiently,exposure times will be long. Because the catadioptric projection systemsof this invention do not require large angles for separating lightincident to and exiting from the concave mirror, the catadioptricprojection systems can have high numerical apertures, thereby reducingexposure times.

Because the first imaging system A and the second imaging system B areindependent of each other, manufacture and alignment are simple.

Having illustrated and demonstrated the principles of the invention in aexample embodiments, it should be apparent to those skilled in the artthat the example embodiments can be modified in arrangement and detailwithout departing from such principles. I claim as the invention allthat comes within the scope of these claims.

1. A catadioptric projection system for receiving light from a reticleand projecting a pattern from the reticle onto a substrate, thecatadioptric projection system comprising: a first imaging system thatforms an intermediate image of an illuminated region of the reticle, thefirst imaging system comprising in order from the reticle and along anoptical axis of the first imaging system, (a) a single-pass lens groupcomprising a first negative subgroup, a positive subgroup, and a secondnegative subgroup, and (b) a double-pass lens group comprising a concavemirror, wherein light from the illuminated region of the reticle passesthrough the single-pass lens group and the double-pass lens group,reflects from the concave mirror, and returns through the double-passoptical group; a first turning mirror placed near the intermediate imagethat receives the light reflected by the concave mirror to and returnedthrough the double-pass optical group; and a second imaging system thatreceives the light reflected by the first turning mirror and thatre-images the intermediate image to form a final image of theilluminated region of the reticle on the substrate.
 2. The catadioptricprojection system of claim 1, wherein the first negative subgroup of thesingle-pass lens group comprises a lens element with a concave surfacefacing the reticle.
 3. The catadioptric projection system of claim 1,wherein the second negative subgroup of the single-pass lens groupcomprises a lens element with a concave surface facing the double-passlens group.
 4. The catadioptric projection system of claim 2, whereinthe second negative subgroup of the single-pass lens group comprises alens clement element with a concave surface facing the double-pass lensgroup.
 5. The catadioptric projection system of claim 1, wherein eitherthe first imaging system or the second imaging system produces amagnification of less than one.
 6. The catadioptric projection system ofclaim 1, wherein the second imaging system comprises a first lens groupand a second lens group, the system further comprising a second turningmirror placed between the first lens group and the second lens group andthat receives light from the first lens group and directs the light tothe second lens group.
 7. The catadioptric projection system of claim 1,further comprising a third turning mirror placed between the single-passlens group and the double-pass lens group and that receives light fromthe single-pass lens group and directs the light to the double-pass lensgroup.
 8. The catadioptric projection system of claim 7, wherein thethird turning mirror and the first turning mirror are arranged so thatthe light incident to the single-pass optical group and exiting thesecond lens group of the second imaging system propagate alongsubstantially parallel axes.
 9. The catadioptric projection system ofclaim 8, wherein the first axis and the second axis are colinear.
 10. Acatadioptric projection system for receiving light so from a reticle andprojecting a pattern from the reticle onto a substrate, the catadioptricprojection system comprising: a first imaging system that forms anintermediate image of an illuminated region of the reticle, the firstimaging system comprising from objectwise to imagewisc imagewise, (a) asingle-pass lens group comprising a first negative subgroup, a positivesubgroup, and a second negative subgroup, and (b) a double-pass lensgroup comprising a concave mirror, wherein light from the illuminatedregion of the reticle passes through the single-pass lens group and thedouble-pass lens group, reflects from the concave mirror, and returnsthrough the double-pass lens group; a first turning mirror placed nearthe intermediate image, the first turning mirror separating the lightpropagating from the double-pass lens group from the light propagatingto the double-pass lens group; and a second imaging system that receivesthe light reflected by the concave mirror and reflected back through thedouble-pass lens group and that re-images the intermediate image to forma final image of the illuminated region of the reticle on the substrate.11. The catadioptric projection system of claim 10, wherein the firstnegative subgroup of the single-pass lens group comprises a lens elementwith a concave surface facing the reticle.
 12. The catadioptricprojection system of claim 10, wherein the second negative subgroup ofthe single-pass lens group comprises a lens element with a concavesurface facing the first turning mirror.
 13. The catadioptric projectionsystem of claim 11, wherein the second negative subgroup of thesingle-pass lens group comprises a lens element with a concave surfacefacing the first turning mirror.
 14. The catadioptric projection systemof claim 10, wherein either the first imaging system or the secondimaging system produces a magnification of less than one.
 15. Thecatadioptric projection system of claim 10, wherein the second imagingsystem comprises a first lens group and a second lens group, the systemfurther comprising a second turning mirror placed between the first lensgroup and the second lens group and that receives light from the firstlens group and directs the light to the second lens group.
 16. Thecatadioptric projection system of claim 14, wherein the first turningmirror and the second turning mirror are arranged so that light enteringthe single-pass lens group propagates along a first axis and lightreflected by the second turning mirror propagates along a second axissubstantially parallel to the first axis.
 17. In a method for projectinga pattern on a reticle onto a substrate in which a first imaging systemreceives light from the reticle and transmits the light through asingle-pass lens group of the first imaging system and a double-passlens group of the first imaging system, the double-pass lens groupcomprising a concave mirror, and reflecting the light from the concavemirror and returning the light through the double-pass optical group,and separating the light propagating from the double-pass lens group andthe light propagating to the double-pass lens group, and directing thelight propagating from the double-pass lens group to a second imagingsystem, an improvement comprising: (a) providing within the single-passlens group, from objectwise to imagewise, a first negative subgroup, apositive subgroup, and a second negative subgroup; (b) forming anintermediate image with the first imaging system between the firstimaging system and the second imaging system; and (c) locating theintermediate image in proximity to a turning mirror that separates thelight propagating from the double-pass lens group from the lightpropagating to the double-pass lens group.
 18. A method for projecting apattern from a reticle onto a substrate, comprising the steps of: (a)providing a first imaging system comprising a single-pass lens groupincluding from objectwise to imagewise, a first negative lens subgroup,a positive lens subgroup, and a second negative lens subgroup; and adouble-pass lens group comprising a concave mirror; (b) transmittinglight from the reticle through the single-pass lens group and thedouble-pass lens group to the concave mirror, and returning the lightreflected from the concave mirror back through the double-pass lensgroup toward the single-pass lens group; (c) separating the lightpropagating through the double-pass lens group to the concave mirrorfrom the light propagating through the double-pass lens group from theconcave mirror; (d) with the first imaging system, forming anintermediate image of the pattern between the first imaging system andthe second imaging system; (e) directing the light propagating from theconcave mirror through the second imaging system; and (f) forming animage of the reticle on the substrate with the second imaging system.19. The method of claim 18, further comprising directing light from thesingle-pass lens group to the double-pass lens group using a firstturning mirror.
 20. The method of claim 19, further comprising directingthe light, reflected by the concave mirror and returning through thedouble-pass lens group, to the second imaging system using a secondturning mirror.
 21. The method of claim 20, further comprising orientingthe first turning mirror and the second turning mirror so that the lightincident to the first turning mirror and the light reflected by thesecond turning mirror propagate along substantially parallel axes. 22.The method of claim 21, further comprising orienting the first turningmirror and the second turning mirror so that the light incident to thefirst turning mirror and the light reflected by the second turningmirror propagate along substantially the same axis.
 23. The method ofclaim 18, further comprising: providing a first turning mirror placedbetween the single-pass lens group and the double-pass lens group; anddirecting light, returning through the double-pass lens group from theconcave mirror, to the second imaging system using the first turningmirror.
 24. The method of claim 23, further comprising: providing thesecond imaging system with a first lens group and a second lens group;providing a second turning mirror between the first lens group and thesecond lens group; and directing light from the first lens group to thesecond lens group using the second turning mirror.
 25. The method ofclaim 24, further comprising: arranging the first turning mirror and thesecond turning mirror so that the light incident to the first turningmirror and the light reflected by the second turning mirror propagatealong substantially parallel axes.
 26. An exposure system for projectingpatterns on a reticle onto a substrate, the system comprising: (a) acatadioptric projection system that receives an illumination flux froman illuminated region on the reticle and forms an image of theilluminated region on the reticle on a corresponding region on thesubstrate; (b) the catadioptric projection system comprising a firstimaging system and a second imaging system, the first imaging systemforming an intermediate image of the illuminated region of the reticle,and the second imaging system serving to re-image the intermediate imageto form an image of the illuminated region of the reticle on thecorresponding region of the substrate; (c) the first imaging systemcomprising from objectwise to imagewise, (i) a single-pass lens groupcomprising a first negative subgroup, a positive subgroup, and a secondnegative subgroup; and (ii) a double-pass lens group comprising aconcave mirror, wherein light from the illuminated region of the reticlepasses through the single-pass lens group and the double-pass lensgroup, reflects from the concave mirror, and returns through thedouble-pass lens group; (d) a first turning mirror situated near theintermediate image, the first turning mirror separating the lightpropagating from the double-pass lens group from the light propagatingto the double-pass lens group; and (e) a reticle scanner and a substratescanner for respectively scanning the reticle and substratesynchronously to allow the caladioptric catadioptric projection systemto project the patterns on the reticle onto the substrate.
 27. Acatadioptric imaging optical system in a projection exposure apparatusthat transfers a pattern on a reticle which is arranged in a first planeonto a substrate which is arranged in a second plane, the systemcomprising: a catadioptric imaging optical sub-system comprising anoptical group to form an image of the pattern, the optical groupcomprising a concave mirror with a first optical axis; and a dioptricimaging sub-system arranged in an optical path between the catadioptricimaging optical sub-system and the second plane to re-image the imageformed by the catadioptric imaging optical sub-system, the dioptricimaging sub-system comprising a second optical axis, wherein the firstoptical axis and the second optical axis are not parallel to each other,the first plane and the second plane are arranged to be parallel to eachother, the optical group of said catadioptric imaging optical sub-systemcomprises a first optical subgroup comprising a third optical axis, anda second optical subgroup comprising the concave mirror and the firstoptical axis, and the second and third axes form a straight opticalaxis.
 28. A catadioptric imaging optical system according to claim 27,wherein the third optical axis and the second optical axis are parallelto each other.
 29. A catadioptric imaging optical system according toclaim 27, wherein the second optical subgroup comprises a negative lensand a positive lens.
 30. A catadioptric imaging optical system accordingto claim 27, wherein said dioptric imaging optical sub-system furthercomprises an aperture stop.
 31. A projection exposure apparatus thattransfers a pattern on a reticle onto a substrate, comprising: anillumination optical system to illuminate the pattern on the reticle;and a catadioptric imaging optical system according to claim 30 to imagethe pattern onto the substrate, wherein a σ can be varied, σ being aratio of a numerical aperture of said catadioptric imaging opticalsystem to a numerical aperture of said illumination optical system. 32.A catadioptric imaging optical system according to claim 27, wherein theimage formed by said catadioptric imaging optical sub-system is aprimary image of the pattern on the reticle.
 33. A catadioptric imagingoptical system according to claim 27, further comprising a first turningmirror arranged in an optical path between the concave mirror and saiddioptric imaging optical sub-system.
 34. A catadioptric imaging opticalsystem according to claim 33, further comprising a second turning mirrorarranged in an optical path between the concave mirror and the firstplane.
 35. A catadioptric imaging optical system according to claim 34,wherein the third optical axis and the second optical axis intersect.36. A projection exposure apparatus that transfers a pattern on areticle onto a substrate, comprising: a catadioptric imaging opticalsystem according to claim 27 , said catadioptric imaging optical systemforms an exposure region on the substrate that is off of the secondoptical axis.
 37. A projection exposure apparatus according to claim 36,wherein the reticle and the substrate are scanned at different speedscorresponding to the magnification of said catadioptric imaging opticalsystem.
 38. A method of imaging a pattern on a reticle which is arrangedin a first plane onto a substrate which is arranged in a second plane,comprising: forming an intermediate image of the pattern on the reticleusing a catadioptric imaging optical sub-system, wherein thecatadioptric imaging optical sub-system comprises an optical groupcomprising a concave mirror with a first optical axis; and re-imagingthe intermediate image formed by the catadioptric imaging opticalsub-system onto the substrate using a dioptric imaging sub-systemarranged in an optical path between the catadioptric imaging opticalsub-system and the second plane, wherein the dioptric imaging sub-systemcomprises a second optical axis, wherein the first optical axis and thesecond optical axis intersect, the first plane and the second plane arearranged to be parallel to each other, the optical group of saidcatadioptric imaging optical sub-system comprises a first opticalsubgroup comprising a third optical axis, and a second optical subgroupcomprising the concave mirror and the first optical axis, and the secondand third optical axes form a straight optical axis.
 39. A catadioptricimaging optical system used in a projection exposure apparatus thattransfers a pattern on a reticle which is arranged in a first plane ontoa substrate which is arranged in a second plane, comprising: acatadioptric imaging optical sub-system in an optical path between thefirst plane and the second plane, the catadioptric imaging opticalsub-system comprising a first optical group with a lens with a firstoptical axis, and a second optical group with a concave mirror with asecond optical axis; and a dioptric imaging sub-system with a thirdoptical axis arranged in an optical path between said catadioptricimaging optical sub-system and said substrate, wherein the first opticalaxis and second optical axis intersect, the second optical axis and thethird optical axis intersect, and the first and third optical axes forma straight optical axis.
 40. A projection exposure apparatus thattransfers a pattern on a reticle onto a substrate, comprising: acatadioptric imaging optical sub-system according to claim 39 , whereinsaid catadioptric imaging optical system forms the pattern on thereticle that is off of the first optical axis onto an exposure region onthe substrate that is off of the third optical axis.
 41. A projectionexposure apparatus according to claim 40, wherein the reticle and thesubstrate are scanned at different speeds corresponding to themagnification of said catadioptric imaging optical sub-system.
 42. Acatadioptric imaging optical system according to claim 39, wherein thefirst and third optical axes are parallel to each other.
 43. A method ofimaging a pattern on a reticle onto a substrate, comprising: passing alight from the reticle through a first optical group comprising a lenswith a first optical axis; forming an intermediate image by a lightpassing through the first optical group and a second optical group, thesecond optical group comprising a concave mirror with a second opticalaxis; and guiding a light having passes through the second optical groupto the substrate by passing the light through a dioptric imaging opticalsub-system with a third optical axis, wherein the first optical axis andthe second optical axis intersect, the second optical axis and the thirdoptical axis intersect, and the first and third optical axes form astraight optical axis.
 44. A method according to claim 43, wherein insaid forming comprises forming a primary image of the reticle.
 45. Amethod according to claim 43, wherein the first and third optical axesare parallel to each other.
 46. A catadioptric imaging optical systemused in a projection exposure apparatus that transfers a pattern on areticle which is arranged in a first plane onto a substrate which isarranged in a second plane, comprising: a first turning mirror arrangedin an optical path between the first plane and the second plane; aconcave mirror arranged in an optical path between the first turningmirror and the second plane; a second turning mirror arranged in anoptical path between the concave mirror and the second plane; and adioptric imaging optical sub-system arranged in an optical path betweenthe second turning mirror and the second plane and comprising an opticalaxis, wherein the first plane and the second plane are arranged to beparallel to each other, and a first reflection surface of the firstturning mirror and a second reflection surface of the second turningmirror are arranged to be non-parallel with each other.
 47. A projectionexposure apparatus that transfers a pattern on a reticle onto asubstrate, comprising a catadioptric imaging optical system according toclaim 46, wherein said catadioptric imaging optical system forms thepattern on the reticle off of the optical axis onto an exposure regionon the substrate off of the optical axis.
 48. A projection exposureapparatus according to claim 47, wherein the reticle and the substrateare scanned at different speeds corresponding to the magnification ofsaid catadioptric imaging optical system.
 49. A catadioptric imagingoptical system according to 46, wherein the optical axis of saiddioptric imaging optical sub-system forms a straight line.
 50. A methodof imaging a pattern on a reticle which is arranged in a first planeonto a substrate which is arranged in a second plane, comprising:reflecting a light from the reticle with a first reflection surface of afirst turning mirror; reflecting the light from the first turning mirrorwith a concave mirror; reflecting the light from the concave mirrorusing a second reflection surface of a second turning mirror; passingthe light from the second turning mirror to the substrate through adioptric imaging optical sub-system having an optical axis; forming anintermediate image of the pattern in an optical path between the concavemirror and the dioptric imaging optical sub-system; and forming an imageof the intermediate image on the substrate by the dioptric imagingoptical sub-system, wherein the first plane and the second plane arearranged in parallel to each other, and the first and second reflectionsurfaces are arranged to be non-parallel with each other.
 51. A methodaccording to claim 50, wherein said intermediate image is a primaryimage of the reticle.
 52. A method according to claim 50, wherein thedioptric imaging optical sub-system comprises an optical axis along astraight line.
 53. A catadioptric imaging optical system used in aprojection exposure apparatus that transfers a pattern on a reticlewhich is arranged in a first plane onto a substrate which is arranged ina second plane, comprising: a catadioptric imaging optical sub-system inan optical path between the first plane and the second plane, thecatadioptric imaging optical sub-system comprising a first optical groupwith a lens with a first optical axis, and a second optical group with aconcave mirror with a second optical axis; and a dioptric imagingsub-system with a third optical axis arranged in an optical path betweenthe catadioptric imaging optical sub-system and the second plane,wherein the first optical axis and second optical axis intersect, andthe second optical axis and the third optical axis intersect the firstand third optical axes are parallel to each other, and the first andthird optical axes form a straight optical axis.
 54. A method of imaginga pattern on a reticle onto a substrate, comprising: passing a lightfrom the reticle through a first optical group comprising a lens with afirst optical axis; forming an intermediate image by a light passingthrough the first optical group and a second optical group, the secondoptical group comprising a concave mirror with a second optical axis;and guiding a light having passes through the second optical group tothe substrate by passing the light through a dioptric imaging opticalsub-system with a third optical axis, wherein the first optical axis andthe second optical axis intersect, and the second optical axis and thethird optical axis intersect, the first and third optical axes areparallel to each other, and the first and third optical axes form astraight optical axis.
 55. A method for projecting a pattern from areticle onto a substrate, comprising: transmitting light from thereticle through a first imaging system, where the transmitted light passthrough a single-pass lens group and a double-pass lens group to aconcave mirror, and the light is reflected from the concave mirror backthrough the double-pass lens group toward the single-pass lens group;separating the light propagating through the double-pass lens group tothe concave mirror from the light propagating through the double-passlens group from the concave mirror; with the first imaging system,forming an intermediate image of the pattern between the first imagingsystem and a second imaging system; directing the light propagating fromthe concave mirror through the second imaging system; and forming animage of the reticle on the substrate with the second imaging system,wherein the single-pass lens group includes from objectwise toimagewise, a first negative lens subgroup, a positive lens subgroup, anda second negative lens subgroup, and the double-pass lens group includesthe concave mirror.
 56. A catadioptric imaging optical system in aprojection exposure apparatus that transfers a pattern on a reticlewhich is arranged in a first plane onto a substrate which is arranged ina second plane, the system comprising: a catadioptric imaging opticalsub-system comprising an optical group to form an image of the pattern,the optical group comprising a concave mirror with a first optical axis;and a dioptric imaging sub-system arranged in an optical path betweenthe catadioptric imaging optical sub-system and the second plane tore-image the image formed by the catadioptric imaging opticalsub-system, the dioptric imaging sub-system comprising a second opticalaxis, wherein the first optical axis and the second optical axis are notparallel to each other, the first plane and the second plane arearranged to be parallel to each other, and the dioptric imaging opticalsub-system further comprises an aperture stop.
 57. A catadioptricimaging optical system in a projection exposure apparatus that transfersa pattern on a reticle which is arranged in a first plane onto asubstrate which is arranged in a second plane, the system comprising: acatadioptric imaging optical sub-system comprising an optical group toform an image of the pattern, the optical group comprising a concavemirror with a first optical axis; and a dioptric imaging sub-systemarranged in an optical path between the catadioptric imaging opticalsub-system and the second plane to re-image the image formed by thecatadioptric imaging optical sub-system, the dioptric imaging sub-systemcomprising a second optical axis; wherein the first optical axis and thesecond optical axis are not parallel to each other, the first plane andthe second plane are arranged to be parallel to each other, the opticalgroup of said catadioptric imaging optical sub-system comprises: a firstsubgroup comprising a third optical axis, and a second subgroupcomprising the concave mirror and the first optical axis, and the thirdoptical axis and the second optical axis intersect.
 58. A method ofimaging a pattern on a reticle which is arranged in a first plane onto asubstrate which is arranged in a second plane, comprising: forming anintermediate image of the pattern on the reticle using a catadioptricimaging optical sub-system, the catadioptric imaging optical sub-systemcomprising an optical group comprising a concave mirror and a firstoptical axis; and re-imaging the intermediate image formed by thecatadioptric imaging optical sub-system onto the substrate using adioptric imaging sub-system arranged in an optical path between thecatadioptric imaging optical sub-system and the second plane, thedioptric imaging sub-system comprising a second optical axis, whereinthe first optical axis and the second optical axis intersect, the firstplane and the second plane are arranged to be parallel with each other,and the dioptric imaging sub-system comprises an aperture stop.
 59. Amethod of imaging a pattern on a reticle which is arranged in a firstplane onto a substrate which is arranged in a second plane, comprising:forming an intermediate image of the pattern of the reticle using acatadioptric imaging optical sub-system, the catadioptric imagingoptical sub-system comprising an optical group comprising a concavemirror and a first optical axis; and re-imaging the intermediate imageformed by the catadioptric imaging optical sub-system onto the substrateusing a dioptric imaging sub-system arranged in an optical path betweenthe catadioptric imaging optical sub-system and the second plane, thedioptric imaging sub-system comprising a second optical axis, whereinthe first optical axis and the second optical axis intersect, the firstplane and the second plane are arranged to be parallel with each other,and the optical group of the catadioptric imaging optical sub-systemcomprises a first subgroup comprising a third optical axis, and a secondsubgroup comprising the concave mirror and the first optical axis, andthe third optical axis and the second optical axis intersect.
 60. Acatadioptric imaging optical system in a projection exposure apparatusthat transfers a pattern on a reticle which is arranged in a first planeonto a substrate which is arranged in a second plane, the systemcomprising: a catadioptric imaging optical sub-system comprising anoptical group to form an image of the pattern, the optical groupcomprising a concave mirror with a first optical axis; a dioptricimaging sub-system arranged in an optical path between the catadioptricimaging optical sub-system and the second plane to re-image the imageformed by the catadioptric imaging optical sub-system, the dioptricimaging sub-system comprising a second optical axis; a first turningmirror arranged in an optical path between the concave mirror and thedioptric imaging optical sub-system; and a second turning mirrorarranged in an optical path between the concave mirror and the firstplane, wherein the first optical axis and the second optical axis arenot parallel to each other, the reticle and the substrate are arrangedto be parallel to each other, the optical group of said catadioptricimaging optical sub-system comprises: a first subgroup comprising athird optical axis, and a second subgroup comprising the concave mirrorand the first optical axis; and the third optical axis and the secondoptical axis intersect.